rust/tests/ui/traits/trait-upcasting/fewer-associated.rs

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//@ check-pass
// issue: 114035
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
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//@[next] compile-flags: -Znext-solver
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#![feature(trait_upcasting)]
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trait A: B {
type Assoc;
}
trait B {}
fn upcast(a: &dyn A<Assoc = i32>) -> &dyn B {
a
}
// Make sure that we can drop the existential projection `A::Assoc = i32`
// when upcasting `dyn A<Assoc = i32>` to `dyn B`. Before, we used some
// complicated algorithm which required rebuilding a new object type with
// different bounds in order to test that an upcast was valid, but this
// didn't allow upcasting to t that have fewer associated types
// than the source type.
fn main() {}